To test these notions, Schulte et al (2004) examined the processing of visual information using redundant targets in alcoholics and healthy controls. Among the authors’ predictions were (a) that interhemispheric parallel processing of information would be compromised in alcoholics relative to controls, (b) interhemispheric transfer time would be prolonged in alcoholics relative to controls, and (c) interhemispheric transfer time prolongation would be greater in older than younger subjects. They observed that the effects of redundant targets were smaller in older alcoholics than in older subjects with or without history of alcoholism suggesting reduced interhemispheric neural summation. Also, the level of performance was associated with callosal size in controls in contrast to alcoholics. A decrease in the size of the corpus callosum was related to prolonged interhemispheric transfer time, and thinning of the corpus callosum occurred in alcoholism and with aging. Others also had reported an interaction between alcoholism and aging for the corpus callosum (Pfefferbaum et al 1996, 2002). There also was an interaction between aging and alcoholism with regard to brain tissue volumes, with volume abnormalities greater in older
